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PET/MRI may reveal MRI-occult inflammation
In a rare anti-vimentin encephalitis case, molecular imaging detected abnormalities that declined alongside neurologic improvement following immunotherapy.
To describe the use of F-18–DPA714 PET/MRI to assess neuroinflammation in a patient with anti-vimentin IgG-associated autoimmune encephalitis and unremarkable initial MRI findings.
Approach:
Case and testing: Researchers reported a man in his late 40s with progressive neurologic symptoms, peripheral nerve abnormalities, and anti-vimentin IgG detected in cerebrospinal fluid but not serum. He underwent conventional MRI, F-18–DPA714 PET/MRI, and functional assessments…
Treatment and follow-up: The patient received IVIG for 5 days followed by monthly subcutaneous ofatumumab. Clinical assessments, antibody testing, and PET/MRI were repeated after 3 months.
Key Findings:
Conventional MRI lacked characteristic corticospinal tract abnormalities, while baseline PET/MRI showed elevated tracer uptake in the mesial temporal lobe, brainstem, and frontal lobes.
At 3 months, tracer uptake decreased in the evaluated regions; follow-up MRI showed no new or active lesions.
Gait instability improved and limb numbness partially resolved. The mRS score changed from 2 to 1, MoCA from 29 to 30, and CASE remained 1.
CSF anti-vimentin IgG remained positive at a titer of 1:10 at follow-up despite clinical improvement.
Electrophysiological testing documented peripheral nervous system involvement; the mechanism and relationship to anti-vimentin IgG remain uncertain.
Interpretation:
The authors described F-18–DPA714 PET/MRI as a potential tool for detecting and monitoring inflammation when conventional MRI lacks characteristic findings. This single case does not establish diagnostic performance or the independent effectiveness of ofatumumab.
Limitations:
Single-patient report with only 3 months of follow-up.
The relative contributions of IVIG and ofatumumab to improvement could not be determined.
The study cannot establish long-term outcomes, relapse prevention, or whether tracer changes reliably reflect disease activity across patients.
Testing could not definitively exclude all potential peripheral nerve-directed autoantibodies.
Conclusion:
The report found reduced PET/MRI tracer uptake alongside short-term clinical improvement, but further investigation is needed to assess the imaging method and treatment outcomes in this disorder.
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